GT40, clutch dragging severely or not completely engaging

Happy Saturday! While driving my clutch pedal went to the floor, if I pumped it I could get enough pressure to limp home which I did.

Got home, bled the clutch with all new fluid, and went for a test drive and the clutch is dragging or not engaging completely. If you give it any power the car will go up in RPMs but not move forward.

Is the clutch shot? Do I need to bleed something besides the nipple on the lower passenger side of the transmission? Do I need to adjust something?

MKI GT40
RBT Transmission

Jamie
P2214
 

Julian

Lifetime Supporter
Do you have a hydraulic throw out? If so I wonder if the initial loss of fluid or pumping has coated the friction disc in hydraulic fluid and it is now slipping.
 
Do you have a hydraulic throw out? If so I wonder if the initial loss of fluid or pumping has coated the friction disc in hydraulic fluid and it is now slipping.
I am not 100% sure to be honest, how can I check or determine if I do?
 

Markus

SPRF40
Lifetime Supporter
Jamie,
you need to search the forum - there is information available.....
Due to the fact that I had htob issues myself I remember too well........


Hope this helps some......

Markus
 
I would consider an external slave cylinder. Went thru 2 internal McLeod ones and got fed up before replacing with an external. No problems in many years since.
 

Bill Kearley

Supporter
Have you seen any fluid at the bottom of your bellhousing, a leak? Sad part is the fact that your foot went to the floor. What I'm getting at !!! Your fluid could be passing in the master or check for fluid at your foot box. Hope you get lucky.
 

Ian Clark

Supporter
Seems like multiple problems simultaneously. We have not experienced a failure of McLeod HTOB with Street Twin Clutch Lit with matching aluminum flywheel ( six installations 450-550hp ) however there were other problems caused by excessive runout in the cast bellhousing supplied with early CAV GT40s. That caused the clutch to drag, heavy cutch pedal and grinding gears when engaging first or reverse gear.

All different problems but made us hyper aware of installation setup and clearances.

The clutch is normally engaged, so has a hydraulic leak completely oiled up the clutch disc or has the HTOB overextended / lodged itself on the pinion snout to keep the clutch pressure plate depressed ( clutch disengaged )? AS Rick said it's R&R time, either way.

There is a safe extension range for the hydraulic throw out bearing. McLeod supplied us with a CNC spacer to take up space in the Ford to ZF application. This prevents the bearing from pumping itself out to far. It will only retract to the point where no force is being applied to the clutch pressure plate. Since the CAV bellhousing was slightly thicker than OE we had to make up an additional spacer to slide up the pinion snout.

In essence the spacer brings the fully retracted HTOB on initial assembly to nearly touching the pressure plate so there is minimum extension of the bearing when you push the pedal.

Please keep us posted on your findings when she's all apart.

Cheers
Ian
 
Have you seen any fluid at the bottom of your bellhousing, a leak? Sad part is the fact that your foot went to the floor. What I'm getting at !!! Your fluid could be passing in the master or check for fluid at your foot box. Hope you get lucky.
No, I have not seen a leak.

I'll look at pulling the master, is there a part number? Just remove the pedal box I assume.
 

Bill Kearley

Supporter
Sorry, I don't know the part numbers for your car. First check for a leak at the master, it may look dry so check inside the pushrod boot if you have one. If you have to remove the master I hope your not a big dude., It can be a tight spot to wiggle out of. If possible just remove the clutch master and avoid bleeding the brakes. There has to be sign of fluid some place.
 
Here's one similar to mine:
 

Ian Clark

Supporter
Jamie, you'll have to verify proper function of all components, hoses and fittings in the clutch circuit. On its' own a defective clutch master cylinder would not hold your clutch open so the car will not move as you described. A borescope might be able to show what's going on inside the bellhousing but the fix will require taking it all apart sorry to say...

Ian
 
Dennis Quella at Pantera Performance Center in Colorado offers an external slave setup .

Ron
Hi:

I had an hydraulic throwout bearing in my car whose bleeding line somehow got fouled and torn apart and dumped all the fluid in a big mess. I replaced it with the Pantera Performance external arrangement and all seems well. Somehow, thought, I suspect your master cylinder may be at fault. On other cars I have had similar failures where the clutch basically fails to disengage completely but there is no external leakage. What happens, I think, is that the fluid seems to move past the internal piston seals so there is little to no pressure generated. I would try replacing or testing the master cylinder first, since it is much cheaper and easier and at worst you will end up with a new master cylinder.
/s/ Chris Kennedy
 

Skip Markley

Supporter
Small block Ford motor I am guessing? If so, you might call Bob Wood at Safir - he has an external slave kit that uses an original recreation cast aluminum bell housing with the external slave. Fits RBT / Quaife transaxles. Nice setup and original design.
 
Started to pull the rear end apart, looks like there was a minor leak for some time. Going to replace the Slave and the Master just for peace of mind, also going to replace the clutch while I am in there.

Any recommendations on clutches for 347 motors pushing 500hp?
 

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